This invention relates in general to thermal spray powder-melt coating applicators, and in particular to an adjustable injector assembly whereby powder introduction to a thermal gas spray for ultimate melting and subsequent substrate deposition is provided by a cooled injector whose injection angle is adjustable with respect to the axial centerline of a thermal gas spray nozzle of the assembly without changing axial or radial locations of the injection point.
Present-day application of a coating to a substrate can be accomplished by introducing the coating in precursor-powder form to a high-velocity flow of hot gas such as that found in plasma coating processes for ultimate powder melting and deposition on the substrate to be coated. A typical coating powder applicator provides a nozzle-directed high velocity flow of the heated gas, while injection nozzles of powder injectors are positioned downstream from the nozzle to introduce powder into the hot gas stream. Because of the meltability of the powder situated within the injectors prior to dispensing, present powder injectors must be located outside of the heat zone of the hot gas flow since, otherwise, the powder would melt within the injectors and would no longer be dispersable for introduction into the gas flow. Beyond not having cooling capabilities, present powder injectors typically are limited to a series of fixed locations with respect to angles and distances as measured from the path of gas flow.
As is apparent from the above description of present thermal spray powder coating applicators, current equipment offers little flexibility and limited versatility in applying a substrate coating derived from a powder precursor. In particular, a first such restriction is found in the absence of injector cooling and its resulting relatively-far placement requirements of the injector from the gas flow which is especially critical where the powder has a relatively low melting temperature. This distance interferes with a more efficient and less materials-loss insertion point closer to the hot gas flow. A second such present restriction is found in the inability to precisely direct a powder injection with respect to its angle and distance within the gas flow for achieving a more controlled coating process.
In view of these limitations as found in the prior art, it is apparent that a need is present for a thermal spray powder coating applicator with a powder injector assembly that provides operational adaptability with respect to precursor-powder introduction into a gas flow designated to carry the subsequently-melted powder to a coatable surface. Accordingly, a primary object of the present invention is to provide a powder injector assembly that permits systematic independent adjustment of powder injection angle along with axial and radial locations using a cooled powder injector which will withstand the high temperature environment and also prevent melting of powder prior to its exit from the injector.
Another object of the present invention is to provide a powder injector assembly wherein the injector element has an injection nozzle in communication with an injection nozzle positioner of the assembly for respective radial, axial, and angular movement of the injection nozzle in relation to the flow of heated gas.
Yet another object of the present invention is to provide a powder injection assembly wherein the injection nozzle positioner is operable independently and incrementally radially, axially, and angularly.
These and other objects of the invention will become apparent throughout the description thereof which now follows.
The present invention is a powder injector assembly for delivering heat-meltable powder into an axial flow of heated gas emanating under pressure from a gas nozzle exit port of a powder coating applicator. The injector assembly comprises a powder injector rotatable in a plane whose centerline is perpendicular to the flow of heated gas from the gas nozzle exit and which is positionable downstream from the gas nozzle exit port for issuing powder into the flow of heated gas. An injection nozzle exit port is integral with and leads from the injector and is disposed in the centerline for angular rotation thereabout, and is alignable with the gas nozzle exit port for issuing powder into the flow of heated gas for melting and subsequent substrate deposition. A cooling system is integral with the injector for removing heat from the injector to thereby maintain the powder within the injector in a non-melted state until its exit into the gas flow. The injector is independently movable laterally, axially, and angularly for respective radial, axial, and angular movement of the injection nozzle exit port in relation to the flow of heated gas. Angular movement of the injector occurs along a centerline passing through the tip of the nozzle exit port to thereby permit independent injection-angle adjustment without changing the axial or lateral location of the injection point.
Because the injector is incrementally and independently movable while the cooling component overcomes location restrictions due to excess heat, an operator can direct powder injection in a most favorable manner with respect to hot gas flow such that a chosen angular injection of powder within a chosen distance radially from the gas flow centerline and axially from the gas nozzle exit port can produce an optimum melted-powder coating result on the substrate. Consequently, powder coatings designed for specific purposes such as such as those charged with wear, corrosion, erosion, and fouling resistance, can be effectively applied to aircraft surfaces, storage tank walls, sensitive electronic instrumentation, and the like where so indicated with broad powder injection flexibilities in accord with particular coating needs and attributes.